[Python-Dev] async/await in Python; v2 (original) (raw)

Yury Selivanov yselivanov.ml at gmail.com
Thu Apr 23 20:02:32 CEST 2015

Hi Barry,

On 2015-04-23 1:51 PM, Barry Warsaw wrote:

On Apr 21, 2015, at 01:26 PM, Yury Selivanov wrote:

The updated version of the PEP should be available shortly at https://www.python.org/dev/peps/pep-0492 and is also pasted in this email. There's a lot to like about PEP 492. I only want to mildly bikeshed a bit on the proposed new syntax. Thanks! Why "async def" and not "def async"?

To my eye 'async def name()', 'async with', 'async for' look better than 'def async name()', 'with async' and 'for async'. But that's highly subjective.

I also read "for async item in iter:" as "I'm iterating iter with async item".

My concern is about existing tools that already know that "def" as the first non-whitespace on the line starts a function/method definition. Think of a regexp in an IDE that searches backwards from the current line to find the function its defined on. Sure, tools can be updated but it is it necessary to choose a syntax that breaks tools? def async useful(): seems okay to me. Probably the biggest impact on the PEP would be symmetry with asynchronous with and for. What about: with async lock: and for async data in cursor: That would also preserve at least some behavior of existing tools. Anyway, since the PEP doesn't explicitly describe this as an alternative, I want to bring it up. (I have mild concerns about a* magic methods, since I think they'll be harder to visually separate, but here the PEP does describe the async* alternatives.)

Anyways, I'm open to change the order of keywords if most people like it that way. Same for async*_ naming.

Thanks! Yury

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